A color sensitive material has the so-called color couplers in at least one of its photographic layers. The color couplers are allowed to react with an oxidized aromatic primary amino color developing agent by the color development of the color sensitive material to produce dyes, such as indophenols, indoanilines, indamines, azomethines, phenoxazines, phenazines and the like, and to form colored images.
In a color photographic process, the subtractive color method is usually employed for color reproduction. Silver halide emulsions which are sensitized selectively to blue, green and red lights are employed in combination with couplers which can form images with their respective complementary colors, namely, yellow, magenta and cyan, respectively. To form a yellow image, acylacetoanilide series couplers, and dibenzoylmethane series couplers may be used. To form a magenta image, pyrazolone, pyrazolobenzimidazole, cyanoacetophenone or indazolone series couplers are mainly used. Phenol series couplers such as phenols and naphthols are mainly used to form a cyan image.
These couplers are usually dissolved in high boiling point organic solvents selected from phthalic acid ester series compounds or phosphoric acid ester series compounds. After the couplers are dissolved, they are incorporated into photographic layers such as light-sensitive silver halide emulsion layers and so on.
Specific examples of the high boiling point organic solvents employed for this purpose are described in U.S. Pat. Nos. 2,322,027, 2,533,514, 3,287,134, 3,748,141 and 3,779,765, German Pat. No. 1,152,610, British Pat. No. 1,272,561, German Patent Application (OLS) No. 2,629,842, and so on.
Usually the development process for such color sensitive materials comprises a color developing step, a bleaching step, a fixing step and a washing step. The development process may utilize the so-called blix processing, wherein bleaching and fixing are combined and achieved simultaneously in the same bath. This blix step has been prevailingly carried out in recent years.
Dye images are formed by subjecting an imagewise exposed color sensitive material to such development processes. During such processes, color couplers develop their colors in areas to the extent that they cannot receive color development-processing and cannot produce dyes, resulting in the formation of color stain. The color stain formed in these areas during the development processing steps will be referred to hereinafter by the term "processing stain". A processing stain is especially likely to be formed during the color development process, especially in the bleaching step. A processing stain in a color sensitive material spoils the quality of the dye image formed. Therefore, the emergence of color sensitive materials in which no processing stain is formed has been desired.
The images produced by dyes have imagewise distributions as a result of such processings and the image may vary in different ways with the lapse of time. For instance, a yellow image formed by color development increases its density with the lapse of time. When this occurs the color balance between yellow and other colors (i.e., magenta and cyan) is broken and the quality of color image formed from these dye images is greatly deteriorated. This phenomenon is hereinafter described by the term "color deepening with the lapse of time". Because of this phenomenon there is a need to produce color sensitive materials free of color deepening with the lapse of time.